Multiple Sources of Riparian Wetland Suspended Solids during Episodic Rain Events: Influence on Uranium Transport

Area of Science:

• Environmental Science
• Geochemistry
• Hydrology

Background:

• Suspended solids are primary vectors for contaminant transport in streams.
• Understanding the dynamic properties of suspended solids during rain events is crucial for contaminant transport studies.

Purpose of the Study:

• To investigate how changes in suspended solids properties during rain events influence contaminant transport.
• To determine the characteristics of suspended solids and their association with uranium (U) contamination.

Main Methods:

• Collection of stream water samples during five episodic rain events downstream from a uranium-contaminated wetland.
• Analysis of suspended particle composition using X-ray Absorption Near Edge Structure (XANES) and Extended X-ray Absorption Fine Structure (EXAFS).
• Quantification of solid-to-liquid uranium ratios.

Main Results:

• Initial suspended particles (Fe-flocs) were rich in Fe, Mn, organic-C, and U(VI), adsorbed to organic matter and Fe-oxides.
• High affinity of uranyl for suspended solids observed, with solid-to-liquid U ratios exceeding 72,000.
• Later suspended solids had lower contaminant concentrations, with increased quartz, kaolinite, and gibbsite content.

Conclusions:

• Suspended solids exhibit dynamic changes in composition and contaminant load during rain events.
• The properties of suspended solids, particularly their organic and mineralogical composition, significantly impact uranium transport.
• Effective management of stream contamination requires understanding the evolving nature of suspended solids.